linux-kernel - [PATCH] mm: kmemleak: Skip check in kmemleak_*

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Date:   Fri, 27 May 2022 11:25:02 +0800
From:   <yee.lee@...iatek.com>
To:     <linux-kernel@...r.kernel.org>
CC:     <patrick.wang.shcn@...il.com>, <Kuan-Ying.lee@...iatek.com>,
        <Andrew.Yang@...iatek.com>, <Sunny.Kao@...iatek.com>,
        <chinwen.chang@...iatek.com>, Yee Lee <yee.lee@...iatek.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>
Subject: [PATCH] mm: kmemleak: Skip check in kmemleak_*_phys when pfn bound is not ready

From: Yee Lee <yee.lee@...iatek.com>

In some archs (arm64), memblock allocates memory in boot time when
the pfn boundary (max_pfn/min_pfn) is not ready. The lowmen checks in
kmemleak_*_phys() drop those blocks and cause some false leak alarms
on common kernel objects.

Kmemleak output: (Qemu/arm64)
unreferenced object 0xffff0000c0170a00 (size 128):
  comm "swapper/0", pid 1, jiffies 4294892404 (age 126.208s)
  hex dump (first 32 bytes):
    62 61 73 65 00 00 00 00 00 00 00 00 00 00 00 00  base............
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<(____ptrval____)>] __kmalloc_track_caller+0x1b0/0x2e4
    [<(____ptrval____)>] kstrdup_const+0x8c/0xc4
    [<(____ptrval____)>] kvasprintf_const+0xbc/0xec
    [<(____ptrval____)>] kobject_set_name_vargs+0x58/0xe4
    [<(____ptrval____)>] kobject_add+0x84/0x100
    [<(____ptrval____)>] __of_attach_node_sysfs+0x78/0xec
    [<(____ptrval____)>] of_core_init+0x68/0x104
    [<(____ptrval____)>] driver_init+0x28/0x48
    [<(____ptrval____)>] do_basic_setup+0x14/0x28
    [<(____ptrval____)>] kernel_init_freeable+0x110/0x178
    [<(____ptrval____)>] kernel_init+0x20/0x1a0
    [<(____ptrval____)>] ret_from_fork+0x10/0x20

This patch relaxs the boundary checking in kmemleak_*_phys api
if max_low_pfn is uninitialzed.

Fixes: 23c2d4 (mm: kmemleak: take a full lowmem check in kmemleak_*_phy)
Signed-off-by: Yee Lee <yee.lee@...iatek.com>
---
 mm/kmemleak.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index a182f5ddaf68..6b2af544aa0f 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1132,7 +1132,7 @@ EXPORT_SYMBOL(kmemleak_no_scan);
 void __ref kmemleak_alloc_phys(phys_addr_t phys, size_t size, int min_count,
 			       gfp_t gfp)
 {
-	if (PHYS_PFN(phys) >= min_low_pfn && PHYS_PFN(phys) < max_low_pfn)
+	if (!max_low_pfn || (PHYS_PFN(phys) >= min_low_pfn && PHYS_PFN(phys) < max_low_pfn))
 		kmemleak_alloc(__va(phys), size, min_count, gfp);
 }
 EXPORT_SYMBOL(kmemleak_alloc_phys);
@@ -1146,7 +1146,7 @@ EXPORT_SYMBOL(kmemleak_alloc_phys);
  */
 void __ref kmemleak_free_part_phys(phys_addr_t phys, size_t size)
 {
-	if (PHYS_PFN(phys) >= min_low_pfn && PHYS_PFN(phys) < max_low_pfn)
+	if (!max_low_pfn || (PHYS_PFN(phys) >= min_low_pfn && PHYS_PFN(phys) < max_low_pfn))
 		kmemleak_free_part(__va(phys), size);
 }
 EXPORT_SYMBOL(kmemleak_free_part_phys);
@@ -1158,7 +1158,7 @@ EXPORT_SYMBOL(kmemleak_free_part_phys);
  */
 void __ref kmemleak_not_leak_phys(phys_addr_t phys)
 {
-	if (PHYS_PFN(phys) >= min_low_pfn && PHYS_PFN(phys) < max_low_pfn)
+	if (!max_low_pfn || (PHYS_PFN(phys) >= min_low_pfn && PHYS_PFN(phys) < max_low_pfn))
 		kmemleak_not_leak(__va(phys));
 }
 EXPORT_SYMBOL(kmemleak_not_leak_phys);
@@ -1170,7 +1170,7 @@ EXPORT_SYMBOL(kmemleak_not_leak_phys);
  */
 void __ref kmemleak_ignore_phys(phys_addr_t phys)
 {
-	if (PHYS_PFN(phys) >= min_low_pfn && PHYS_PFN(phys) < max_low_pfn)
+	if (!max_low_pfn || (PHYS_PFN(phys) >= min_low_pfn && PHYS_PFN(phys) < max_low_pfn))
 		kmemleak_ignore(__va(phys));
 }
 EXPORT_SYMBOL(kmemleak_ignore_phys);
-- 
2.18.0